Doubly tunable femtosecond source offers spectroscopists a new tool
Researchers at the Rutherford Appleton Laboratory (Didcot, England) have developed a laser system that generates two synchronized but independently tunable femtosecond pulses in the visible spectrum. The laser is designed for use in a range of pump-probe spectroscopic techniques. The system is based on two optical parametric amplifiers (OPAs) that are both seeded by a single white-light continuum source and pumped by the second harmonic of a Ti:sapphire regenerative amplifier (Spitfire, Spectra-Physics Lasers, Mountain View, CA). The system produces 100-200-fs, 15-µJ pulses at 800 nm with a repetition rate of 40 kHz. Angle-tuning of the OPAs generates pulses over a spectral range from 480 to 750 nm with bandwidths of 10 nm and energies of about 50 nJ per pulse. Frequency-mixing with the 800-nm fundamental and frequency-doubling the signal and idler outputs of the OPAs extend system tunability into the UV. Prism pulse compression reduces the cross correlation between the OPAs from around 500 to 150 fs (FWHM).